Human engineered imaging optical systems are typically laid out like a ‘camera eye’ or vertebrate eye: a single imaging lens and a focal plane where a fairly high-resolution image is formed. The camera eye demands a fairly large volume for the incoming radiation to come to focus in the focal plane. The behavior and optics of the camera lens is well understood today. In some applications the resolution and the sensitivity is balanced against other advantages such as device mechanical flexibility, larger depth of focus, and larger field of view. Recent improvements in low cost image sensors allow digital cameras to be made smaller and designed more flexibly.
Another design is based on concepts of a compound eye, as found in many insects. A compound eye sensor has a large number of small, independent facets with sub-millimeter diameter, each combined with a low cost image sensor. Compound eye sensors can be divided into apposition and superposition compound eyes. In apposition compound eyes, each facet, or lens, directs light onto a single, corresponding light-detecting element. In superposition compound eyes, multiple facets or lenses direct light onto a particular light-detecting element. Both eye types can use refractive or reflective mechanisms for forming images.
Existing approaches for constructing compound eyes can cause misalignment errors of the optical components (i.e., the lenses) with respect to the electronic components (i.e., the image sensors). Other problems, such as aberration and resolution degradation arise from the planar geometry of existing compound eyes.